In the control of internal combustion engines, the conventional practice utilizes electronic control units, volatile and non-volatile memory, input and output driver circuitry, and a processor capable of executing a stored instruction set, to control the various functions of the engine and its associated systems. A particular electronic control unit communicates with numerous sensors, actuators, and other control units necessary to effect various control and information functions of the engine and/or vehicle.
Various sensors are used to detect engine operating conditions which may affect control of the engine and/or vehicle. To provide information to the operator relative to engine operating conditions and/or control the engine based on current engine operating conditions, conventional practice utilizes an engine operating parameter such as a coolant temperature or pressure, and compares the engine operating parameter with a limit which may vary as a function of a different engine operating parameter, such as throttle position, engine speed, or engine torque. If the engine operating parameter drops below the limit, the engine may automatically shut down, without first informing the operator, to protect the engine from damage.
Depending upon the particular engine or vehicle operating conditions, it may be undesirable to shut down the engine without first providing the vehicle operator an opportunity to take corrective action, or to override the requested engine shutdown. Furthermore, it is desirable to have sufficient confidence in the accuracy of sensor signals and other indicators which provide signals indicative of current engine operating conditions so that operator information or subsequent engine control is reliably performed.
Some prior art control systems provide a pressure limit or threshold as a function of engine speed. However, such systems may experience false alarms shortly after engine start-up or during other transient conditions where engine fluid pressures vary rapidly.